Increasing environmental concerns regarding the disposal of animal manure, for example and without limitation cow manure, pig manure, chicken manure, turkey manure, duck manure require new and innovative methods of disposal. Animal farming has rapidly moved toward concentrated feeding operations which produce large volumes of manure in a relatively small area. Historically, the manure has been spread over adjacent fields or transported to nearby farms. The ever increasing concentration of nutrients in the soil, which accompanies such practice, presents certain issues related to soil pollution, air pollution, and water pollution. The US Environmental Protection Agency (EPA) has produced regulations and requirements for Concentrated Animal Feeding Operations (CAFO) to address these issues.
Current dairy farming operations are moving toward farms which have increasing numbers of animals, concentrated in high density animal feeding operations. These high animal densities create environmental and social concerns which have led to the increasing regulation of manure management. Soil contamination, ground water pollution, and odor problems resulting from such feeding operations, where a relatively large number of animals are maintained in a relatively small area, are thus of increasing social concern.
Some conventional manure management systems presently in use in combination with high animal density environments, rely on a process which involves methane digesters. Such systems use anaerobic processes to produce methane gas. The methane gas is captured from the anaerobic digestion of the manure; and the gas is then burned as a fuel. While these systems do produce some usable energy, a large fraction of the volume of the manure feed stream is left after such methane gas extraction, and must be disposed of. Namely, the volume of material which still needs to be disposed of is a substantial fraction of the volume, typically substantially the same as the volume of, the raw manure feed stream.
The solids volume can be reduced at e.g. 70% water by weight by squeezing the manure in a press. However, the resulting products are a contaminating effluent, and a smaller, but still substantial, solids volume, in the form of a manure cake. The effluent is a pollution source. Similarly, the pressed solids cake is also a pollution source, which is commonly spread in farm fields.
In addition, in such anaerobic systems, which are directed toward managing large volumes of manure, which is created from a highly-concentrated population of animals, the raw manure, in generally liquidous form at about 16% solids by weight, is stored in covered earthen pits, or in concrete closed storage tanks while being processed. Storing liquid manure in such anaerobic environment results in the generation of methane, hydrogen sulfide, and other gases. Such gases are accompanied by substantial odor intensity, which is commonly considered problematic.
Thus, there is a need for a new manure management system which further addresses certain of the above issues.